Recording head and process of recording



Sept. 12, 1939. A. DE MADALER ET AL 2,173,051

RECORDING HEAD AND PRocEsS OF RECORDING Filed Aug. 26, 1936 I 1 '19 n'53 k 1 91 :Wm

31 g I i 11 INVENTORS ATTORNEY mans... 12, 1939 RECORDING HEAD ANDPROCESS or I rmcoanme Arthur De- Madaler, Bayport, and William L.

Woolf, Bayside. Long Island, N. Y., assignors to Film RecordingCorporation,- a corporation of New York -'Application August 26, 1936,Serial No. 98,106

25 Claims.

device for recording a groove in a solid medium, the groove having awave pattern with excursions from a straight line corresponding inamplitude,

frequencyandshapeto the pattern of the electric'waves forming them".When so. used this device is'known as a cutting head. It will beapparent to those skilled in the art that such a device may be used inthe reverse manner, namely, to generate electrical impulsescorresponding in frequency and amplitude to the wave pattern ,of agroove recorded in a? solid medium; when so used this device is commonlyknown as an electric v pickup. One object of this invention is to devisean instrument that will be-finore sturdy and less sub-. ject to gettingout of order than those heretofore 3 available.

Another object is to devise an instrument that will form records withless needle scratch than those heretofore in use.

A still further object is to provide an instrument that records a grooveof great durability permitting many reproductions with a minimum ofdistortion.

A'more specific object is to devise an instrument capable of making arecord of good quality on a strip of film, particularly a film moving atthe rate of speed commonly employed in moving picture practice, namely,from approximately 6 inches per second in the case of 16 m. m. film to18 inches per second in the case of m. m. films.

.In this device a groove is formed by a recording point pressing into amoving medium. The 35 recording point is not movable in the direction inwhich the groove-carrying medium moves, but is capable of motionsubstantially at right angles thereto. The recording point is mounted inthe end of a stylus which is rigidly connected to a rotary member. Theoscillation or vibration of the rotary member causes correspondingvibration or oscillation of the recording point. To facilitate thevibration of the rotary member it is mounted on knife edges and providedwith springs which restore it to its original position when displacedtherefrom. Displacements are caused by thrusts transmitted through aconnecting pin from a vibrating armature to a rocker arm rigidlyattached to the rotary member.

0 The construction and operation of this device will be readilyunderstood by referring to the drawing in which like numbers refer tolike parts.

Figure 1 is a top view of the improved recording head.

Figure 2 is a side elevation.

This invention relates to an electro-mechanical Figure 3 is a section online 3-3 of Figure 2. Figure 4 is a fragmentary perspective view showingthe recording unit. g In this device a cutting point I is mounted in oneend of a stylus 2, the other end of the 5 stylus'being rigidly attachedto a rotary member 3 which is supported on knife edges 4; the rotarymember 3 is held tightly against the knife edges by springs 5. A rockerarm 9, also rigidly attached to rotary member 3, receives impulses 10from an armature M through a connecting rod l0 causing the recordingpoint I to transcribe a wavy line on a film 24 moving on a sprocketwheel 22. The needle point I is embedded in the film to a depth of .002inch.

In the preferred embodiment ofthe invention the recording point I is apolished diamond. The stylus 2 is designed in cross-section and made ofa material to afford the maximum possible rigidity with the minimumpossible mass; parm ticularly is it desirable to limit the mass of thestylus in the end remote from the rotary member. The stylus should notbe subject to internal vibration but should vibrate only as a whole inunison with the rotary member which drives it. 25 In the preferredembodiment of this device the stylus is oval in cross-section, the longaxis of the oval lying in the plane perpendicular to the'plane of therotary member. This stylus is also tapered, diminishing in cross-sectionas it apa proaches the recording point. We have also employed hollowstylus models, and stylus models made of Duralumin as well as-steel, orBakelite.

It is preferable to slant the stylus forward from the rotary member, thepreferred angle between a thembeing approximately sixty degrees.

The rotary member 3 is formed with slots or grooves I! which bearagainst and provide seats ;'for the knife edges 4. Boththe slots orgrooves and the knife edges are polished and hardened. o The rotarymember 3 may be made hollow to reduce the mass or may be made of solidmaterial. It has also been made from Duralumin as well as steel, wood,metal, brass, etc. Duralumin models have been v employed fitted withsteel bearing 45 surfaces for the knife edges. The knife edges are heldin place and supported by pins 8 which fit snugly into holes drilledinto the body of the device. 'These pins may be further secured by setscrews Bshown in Figure 3. In the preferred n embodiment of this devicethe knife edges are either complete circles or segments thereof and maybe turned about the pins 8 as an axis in order to supply new bearingedges against the crushed or worn. The pins 8 are sufliciently tight toprevent vibration but loose enough to permit rotation of the knife edgesby the application of sufficient force without shearing off.

In the preferred embodiment of this invention the springs 5 are curvedin form and act as cantilevers. One end of each spring is attached tothe rotary member 3 by screw 6. The opposite end of each spring is heldby an adjustable screw 7. The springs 5 are so placed that the stressesgenerated in them by tightening the screws I tend to rotate the rotarymember in opposite directions. In the drawing only two springs areshown. More springs may be employed, if desired. As the screws 1 aretightened the stresses in the springs are increased. By this means thevibrating portion of this device is tuned so that the natural period ofthe vibrating portion of the device may be tuned to any frequencydesired.

In practical operation it is preferable to tune the apparatus to a highpitch.

The usual commercial loud speakers of the day through which recordingsmade by the device are reproduced, have a tendency to attenuate highfrequencies. In order to overcome this tendency we have found itdesirable to over-record the high frequencies by the same amount whichthe reproducer system attenuates them. This practice has an addedadvantage of minimizing needle scratch. 7 It is important that thesprings be capable of withstanding suflicient strain to cause the systemto vibrate naturally at very high frequencies. This requires a springsystem of great stiffness and the requisite stifiness is provided by theconstruction described. By curving the springs through a wide angle asshown in Figs. 3 and 4 we have found that the resistance of the springsystem to motion of the stylus is substantially proportional to theangular displacement within the limits of the displacement employed inrecording, viz. about two tenths of one degree. Springs have beenemployed varying in curvature from 180 to 360 degrees.

The resistance ofiered by the spring mounting is consequentlyyery largecompared with the force exerted on the stylus when the cutting point iscutting the groove in the record and thus the device is comparativelyfree from resonant peaks.

The slots or troughs I 2 may be milled across the entire length of therotary member 3 or may be segments only near the ends of the rotarymemher. If in segments care must be exercised to see that their axes liein the same straight line. A projecting lug I3 is rigidly attached tothe device and provided with threads for engaging one of the screws 1. Aportion of the material of the device is cut out to provide a recess forthe other adjusting screw I. An armature I4 is centered with one endmid-way in the gap provided by pole pieces I5 and I6 and the other endmidway in the gap provided by pole pieces I! and I8.

It will be noted that the tightening of one of the screws i will pullone end of the armature ll to the right, while the tightening of thescrew 1 in the other spring will pull that same end of the armature tothe left. By a proper setting of these screws one end of the armature iscentered mid-way between the pole pieces l5 and I6 and the other end ofthe armature opposite the connecting pin is centered between pole piecesI! and I8. By adjus ing the relative positions of the screws I thesystem is balanced. By tightening or loosening both screws I withoutchanging their relative positions-with respect to each other, the systemis tuned. By making the springs sufliciently long and curving themthrough a wide angle the stillness of the system remains constant withinthe limits of its normal vibration.

The rocker arm 9 which is attached to the ratary member 3 is alsodesigned to be stiif, light. strong and free from vibration withinitself so that any vibration transmitted to it by the connecting rod IIIis transmitted without distortion to the rotary member 3 and thence tothe stylus 2. The rocker arm 9 is tapered, increasing in cross-sectionfrom the connecting rod M to the rotary member 3. It is also oval inshape, the long axis lying approximately in the same plane as theconnecting rod Ill. The rocker arm may be made hollow to reduce mass. Itmay be made of steel or lighter material. We have employed successfullymodels in which the rocker arm ti, rotary member 3 and stylus 2, wereall made in one piece, steel having been employed in some models andDuralumin in others.

The rocker arm 9 is placed forward on the rotarymember 3 between thesprings 5 and knife edges 4, causing the stresses of vibration to betransmitted through a portion of the rotary member 3 as well as throughthe rocker arm ii and the stylus 2. By this means there is a. tendencyto decrease the noise transmitted through the system.

The ratio of the vertical distance of the connecting rod Ill from therotary member (which is approximately the length of the rocker arm) tothe vertical distance from the recording point to the rotatry member(which is the length of the stylus time's the sine of the angle includedbetween the stylus and the rotatry member) is of great importance. Ifthis ratio is unity, the distance of travel 01 the end of the armatureis equal to the distance of travel oi the recording needle. If the ratiois less than unity the record'- ing needle moves a lesser distance thanthe armature. By this means the needle may be made to move through therecord medium by applying to the armature a force less than that whichthe resistance of the record medium offers to the needle. If this ratiois greater than unity the recording needle will move further than thearmature. By this means, provided adequate recording power is available,high notes of small amplitude may be recorded which otherwise may belost due to thetendency of the medium to flow under the needle pressure.Variations in this ratio may be made to give variations in the tonequality of the recording, and may be made to compensate for variationsin the record medium. It is preferable to dampen the connecting rod IDwith a piece of rubber damping material I I. The connecting rod l0should be made of thin, light material. By making the rod sufficientlysmall in diameter it may be made to absorb a portion of the noise whichwould otherwise be transmitted' through it from the armature. Theconnecting ro'd must not be sufficiently thin, however, to set upvibration and noise of its own nor sufficiently thin to absorb desirablehigh frequencies transmitted from the armature. In the preferredembodiment of this invention the connecting pin is .030 inch indiameter.

The armature I4 is supported in position by an armature spring II.

The armature spring 3| is made sumciently rigid to prevent motion of thearmature as a whole from right to left, but is flexible to rotary motionof the armature. In the preferred embodiment 01' this invention thisspring is made of Phosphor bronze. This spring is held in posi-.structure of the device.

tion by screws 32 and 33 threaded into struts I1 and 38' attached to thepole pieces. Pole pieces I6 and I. on one side of the; armature areof-like polarity being attached to the same pole of the magnet 30,forming the main supporting Pole pieces I and II on the opposite side ofthe magnet are of like polarity, but of opposite polarity to I 6 and I8,both being attached to the opposite pole of the magnet 30. The armatureI4 is surrounded by two coils l9 and 20 electrically connected to eachother so that a current passing through the coils in one direction willmagnetize the armature with one polarity and a current passing throughthe coils in the opposite direction will magnetize the armature with thepolarity ,of the opposite direction, the magnetizing forces of the twocoils assistingeach other. If poles I6 and I8 are south poles and ifpoles I5 and II are north poles and if the current is passing throughthe coils in such direction as to make the upper end of the armaturenorth and the lower end south, the

- armature will tend to rotate about the spring 3| in a clock-wisedirection (Figure 2) causing the recording point I to move toward theleft. If. the

current through the coil is reversed the armature will be magnetized inthe opposite direction and a cause it to rotate in a counter-clockwisedirection, forcing'needle point I to move to the-right.

If the needle point is removed from its central position as a result ofa current in the coil it will be restored to its original position bythe springs when the current disappears. If an intermittent directcurrent or an alternating current be impressed upon the coil the cuttingpoint I will vibrate in synchronism with the interruptions of the directcurrent or with the reversal of the direction of the alternating currentIf the current is modulated with voice or music frequencies the needlewill vibrate with like frequencies and corresponding amplitudes, and cuta groove having corresponding characteristics.

In one form of this invention a thrust bearing II is provided torestrain the rotary member 3 against motion in the direction of themotion of the record medium 24. This bearingmay be formed by sharpeningthe forward end of. the

4 in the troughs l2 of the rotary member 3. It

is also desirable to have the springs 5 attached to the rotary member 3by means of screws 6 on this same straight line or axis.

While this device may be used for recording on any phonographic recordmade of such materials as acetate, wax,-aluminum, etc., it isparticularly adapted to recording on a film. When so used a strip offilm 24 is threaded over the sprocket wheel 22, the perforations in thefilm engage the teeth of the sprocket wheel and-under the rollers 23which-hold the film against the sprocket. As the mm 24 moves forward inthe direction of the, arrow shown in Figure 4, the recording point Icarves a groove 25 in the film 24. If no electrical impulses are passingthrough the coils I! and 20, the groove-will be a straight line, but ifelectrical impulses of audio Irequency pass through the coil the groovewill be a wavy line having frequency and amplitude characteristicscorresponding to such impulses.

' memberin one direction and the stressesinthe-r' an electro-magnet coilprovided with a soft iron core and carrying direct electric current aswill be well understood by those conversant with the art.

The coils I9 and 20 are prevented from pressing against the armaturespring 3| by coil spacing blocks 34 held in place by screws 35.

The stiffness of the system may be understood from the following: byapplying a force of one half pound to'the stylus at right angles to therotary member 3 and at a point one half inch in vertical distance fromthe line joining the point of contact of the knife edges with the rotarymember, the point is deflected approximately .002-of an inch. Therigidity of this system makes it very stable. These devices have beenused constantlyfor several months with rough handling. and have neverhad to be rebalanced in any way. In this device, very high needlepressures are employed, reaching intensities of the order of 70,000pounds per square inch. This is achieved by concentrating a pressurewith a vertical component of. approximatelyone half pound on a needlepoint, the cross-sectional diameter of which is .003 of an inch at thesurface of the medium. This point is ground at an angle of approximately45 degrees and with, a ball point of .002 inch diameter. By forcing theneedle into the medium to a depth of .002 inch the groove is .003 of aninch wide at the top. The high pressure employed on the needle pointcompresses the material making the groove walls very. dense and highlypolished. The high polish reduces the needle scratch and the greatdensity of the groove walls as well as the fact that the While thepreferred embodiment of the invention has been described in detail, itshould be understood that the invention is not restricted to the precisedetails here described, but may be carried out in other. ways.

Weclaim as our invention:

1. In a'recording head, a recording point, an actuating stylus therefor,a rotary member, said stylus being rigidly attached to and actuated bysaid rotary member, knife edges for supporting said rotary member, aplurality of cantilever springs attached to the rotary member; thestresses in a number of said springs serving to rotate the rotary memberin one direction, and the stresses in the remainder of said springsserving to rotate the rotary member in the opposite direction. v

'2. In a recording head, a recording point, an actuating stylustherefor, a rotary member, mounted on knife edges -said stylus beingrigidly attached to and actuated by said rotary member, a plurality ofcantilever springs secured to the rotary member; the stresses in anumber of said springs being disposed to turn-the rotary" remainder ofsaid springs being disposed to turn the rotary member in the oppositedirection,

means for setting the rotary member in a pre-' determined angularposition with respect to the knife edges by adjusting the positions ofthe ends of the cantilever springs remote from the rotary member.

3. In a recording head, a recording point, an actuating stylus therefor,a rotary member, supported on knife edges, rigidly attached to andactuated by said rotary member, a plurality of cantilever springsattached to the rotary member; the stresses in a number of said springsserving to turn the rotary member in one direction, and the stresses inthe remainder ot' said springs serving to rotate the rotary member inthe opposite direction means for controlling the tension in the springstending to rotate the rotary member in one direction, and independentmeans for varying the tension in the springs tending to rotate therotary member in the opposite direction, permitting the tension in bothsets of springs to be increased or decreased without changing theirtension with respect to each other and without varying the angularposition of the rotary member with respect to the knife edges.

4. In a recording head, a recording point, an actuating stylus therefor,a rotary member, said stylus being rigidly attached to and actuated bysaid rotary member, a plurality of 1 cantilever springs attached to saidrotary member; the stresses in a number of said springs being,disposedtorotate the rotary member in onedirection and the stresses in theremainder of said springs being disposed to rotate the rotary member inthe opposite direction; means for varying. the tension of said springs,said springs being capable of withstanding suflicient stress to permitthe vibrating portion of the system to be tuned to any resonantfrequency between 500 and 15000 cycles per second.

'5. In a recording head, a recording point, an actuating stylustherefor, a rotary member supported on knife edges, said stylus beingrigidly connected to said rotary member, a rocker arm rigidly attachedto said rotary member, a connecting rod attached to the end of saidrocker arm opposite the rotary member, said connecting rod disposedwithin a plane substantially at right angles to the plane containing therotary member, the end of said connecting rod opposite the rocker arm'being attached to an armature adapted tovibrate in unison with soundimpulses.

6. In a recording head, a recording point, an actuating stylustherefor,-a rotary member supported on knife edges, said stylus beingrigidly connected to said rotary member, a rocker arm rigidly attachedto said rotary member, and a rubber damped connecting rod connectingsaid rocker arm to an armature adapted to vibrate in unison with soundimpulses.

'1. In a recording head, a recording point, an actuating stylustherefor, a rotary member mounted on knife edges, said stylus beingrigidly connected to said rotary member, a rocker arm rigidly attachedto said rotary member, an armature susceptible to vibration in unisonwith sound impulses, a rubber damped connecting rod connecting saidrocker arm to said armature, said connecting rod being sufficiently thinto absorb sound impulses of scratch noise frequency.

8. In a recording head, a recording point, an

actuating stylus therefor, a rotary member mounted on knife edges, saidstylus being rigidly connected to said rotary member, a rocker armrigidly attached to said rotary member, an armature suspended in amagnetic field, and surrounded by a coil adapted to vibrate at audiofrequencies in unison with electrical impulses in said coil, and aconnecting rod attached to said armature and to said rocker arm.

9. A device of the type described comprising two coils, electricallyconnected, susceptible to electrical impulses of audio frequencies, anarmature suspended within said coils by a flexible spring disposedbetween said coils, the two ends of the armature disposed in two airgaps, each gap being formed by two poles, the two poles on one side ofsaid armature being of like polarity, and of opposite polarity from thetwo poles on the opposite side of said armature; a source of magneticenergy to magnetize said poles, a rotary member supported on knifeedges, cantilever springs attached to said rotary member, for restoringthe rotary member to a fixed angular position, a rocker arm rigidlyconnected to said rotary member, a connecting rod between one end ofsaid armature and said rocker arm, and a stylus, rigidly connected tosaid rotary member.

10. In a recording head, a rotary member supported on knife edges, saidknife edges being circularly curved, and a recording point carried bysaid rotary member. v

11. In a recording head, a rotary member supported on knife edges, saidknife edges being in the form of a complete circle, and a recordingpoint carried by said rotary member.

12. In a recording head, a rotary member, a plurality of curvedcantilever springs secured to said rotary member, the stresses incertain of said springs operating to turn the rotary member in onedirection, the stresses in the other springs operating to turn therotary member in the opposite direction, a stylus rigidly secured to therotary member, and .a recording po nt carried by said stylus.

13; Ina recording head, a rotary member, a plurality of curvedcantilever springs secured to said rotary member, said springs beingcurved through an angle not less than 180 degrees, the stresses incertain of said springs operating to turn the rotary member in onedirection, the stresses in the other springs operating to turn therotary member in the opposite direction, a stylus rigidly secured to therotary member, and a recording point carried by said stylus.

14. In a recording head, a rotary member, a plurality of curvedcantilever springs secured to said rotary member, the stresses incertain of said springs operating to turn the rotary member in onedirection, the stresses in the other springs operating to turn therotary member in the op- Y posite direction, the resistance offered bysaid springs to the rotation of said rotary member being approximatelyproportional to the angular displacement of said rotary member from itsposition of rest when said angle of displacement does not exceedtwo-tenths of one degree, a stylus rigidly secured to the rotary member,and

a recording point carried by said stylus.

15. Ina recording head, a rotary member provided with a trough andsupported by a plurality of knife edges bearing in said trough, saidrotary member being attached to a plurality of springs, the stresses incertain of said springs serving to rotate the rotary member in one direcm 'tion, the stresses in other of said springs serving vided with aplurality of trough segments, the

axis of which all lie in the same straight line, a plurality ofknife'edges bearing in said trough segments for pivotally supportingthe. rotary member, said rotary member being attached to a plurality ofsprings, the stresses in certain of said springs serving to rotate therotary member in one direction and the stresses in others of saidsprings serving to rotate said rotary member in the opposite direction,and a stylus, carrying a recording point, rigidly secured to said rotarymember.

17. In a recording head, a rotary member supported on knife edges, arocker arm rigidly attached to said rotary member, means for impai tingvibrations of audio frequency to said rocker arm, and a stylus, providedwith a recording point, rigidly secured to said rotary member.

18. In a recording head, a rotary member supported on knife edges, arocker arm rigidly attached to said rotary member, an armature, aconnecting rod, one end of which is attached to said rocker arm andthe-other end of which is connected to said armature, and a stylus,provided with a recording point, rigidly secured to said rotary member.

19. In a recording head, a rotary member supported on knife edges, astylus, provided with a recording point, rigidly secured to said rotarymember, a rocker arm rigidly attached to said rotary member, anarmature, a connecting rod,

one end of which is attached to said armature and the other end of.which is attached to said rocker arm at a point, the vertical distanceof which to a straight line drawn between the points of contact of theknife edges with said rotary member is greater than the verticaldistance from the recording point to the said line.

20. In a recording head, a rotary member supported on knife edges, astylus, provided with a recording point, rigidly secured "to said rotarymember, a rocker arm rigidly attached to said rotary member, aconnecting rod, one end of which is attached to an armature and theother end of which is attached to said rocker arm at a point, thevertical distance of which to a straight line drawn between the pointsof contact of the knife edges with said rotary member is less than thevertical distance from the recording point to the said line.

21. In a recording head, a rotary member supported on knife edges, astylus, having a recording point, rigidly carried by said rotary member,a rocker arm rigidly attached to said rotary member, an-armature, aconnecting rod, one end of which it attached to said armature and theother end of which is attached to said rocker arm at a point, thevertical distance of which to a straight line drawn between the pointsof contact of the knife edges with said rotary member is equal to thevertical distance from the recording point and the said line.

22. In a recording head, a rotary member supported by knife edges, astylus having a recording point, rigidly attached to and actuated bysaid rotary member, said rotary member being attached to a plurality ofcantilever springs, the stresses in certain of said springs servingtorotate the rotary member in one direction, and the stresses intheremainder of said springs beingdisposed to rotate the rotary memberin the opposite direction, means for controlling the stresses in saidsprings tending to rotate the rotary member in one direction, and anindependent means for varying the stresses in the springs tendingtorotate the rotary member in the opposite direction, both said meanspermitting the stresses in both sets of springs to be increased ordecreased without varying the angular position of the rotary member withrespect to the knife edges.

, 23. In a recording head, a rotary member supported on knife edges, astylus haying a recording point, rigidly attached to and actuated bysaid rotary member, a rocker arm rigidly attached to said rotary member,an armature, a rubber damped connecting rod connecting said rocker armto said armature and capable of vibrating in unison with sound impulses.said connecting rod having a diameter not greater than 30 thousandths ofan inch.

24. In a recording head, a rotary member supported on knife edges, astylus, having a recording point, rigidly secured to said rotary member,springs attached to said rotary member capable of offering a forceresistant to rotary motion to the amount of eight ounces, appliedone-half inch from the axis of rotation of said rotary member when theangular displacement of said rotary member does not exceed two tenths ofone degree.

25. In a recording head, a rotary member, supported by knife edges, astylus, having a recording point, rigidly secured to said rotary membersaid rotary member being attached to a plurality of cantilever springs,the stresses in a numberof said springs being disposed to rotate therotary member in one direction, and the stresses in the remainder ofsaid springs being disposed to rotate the rotary member in the oppositedirection, said springs being capable of tuning to sucha stiflness thata force-of eight ounces applied perpendicularly to and one-halt inchfrom a line drawn through the points of contact of said knife edges withsaid rotary member, will not deflect said point at which said force isapplied more than .002 inch.

m-rmm DE MADALER. WILLIAM L. woorr.

